To identify a critical cardiopulmonary bypass (CPB) duration threshold predictive of a complicated postoperative course after elective cardiac surgery in the absence of technical complications and to find early postoperative predictors within the high-risk group.

Single-center retrospective cohort study.

An urban teaching hospital.

A total of 150 adults undergoing elective cardiac surgery with CPB. Patients with intraoperative technical surgical complications were excluded.

Not applicable (standard clinical care).

A combined endpoint (in-hospital mortality; prolonged mechanical ventilation >12 hours; renal replacement therapy; neurologic complications: confusion, delirium, obtundation; requirement for norepinephrine >24 hours) defined an unfavorable postoperative course. Receiver operating characteristic curve analysis identified a CPB duration of ≥132 minutes as a specific (93%) predictor of the endpoint. Within this prolonged CPB cohort (n = 35), patients who developed complications had significantly higher immediate post-CPB leukocyte counts and lactate levels. The product of these values (Lactate × Leukocytes, in 10⁹ × mmol × L^–2) demonstrated high prognostic utility. A threshold of ≥72 × 10⁹ × mmol × L^–2 predicted the combined endpoint with an area under the curve of 0.909 (sensitivity 100%, specificity 81%) and strongly correlated with the duration of postoperative mechanical ventilation (rho = 0.86, p < 0.0001).

In the absence of technical surgical complications, a CPB duration ≥132 minutes signifies increased risk. For these patients, the simple product of immediate post-CPB lactate and leukocyte count is a powerful, readily available early predictor of a complicated postoperative course, potentially outperforming CPB duration alone and reflecting the combined pathophysiology of systemic inflammation and impaired perfusion.